Duddridge served as Chairman of the WellsYoung Conservatives from 1989 until 1991, and was elected Chairman of Essex University's Conservative Association in 1990. In 1991, Conservative MP Bernard Jenkin appointed him as a researcher.

After graduating in 1993, Duddridge embarked upon a retail and merchant banking career with Barclays until 2005. The company posted him to Africa with the Bank of Swaziland between 1995 and 1996, before he went on to be sales director for Banque Belgolaise in Ivory Coast until 1998. Duddridge returned to the UK in 1998 as Barclays national sales manager, and was seconded as service delivery director by Barclays Bank of Botswana in 2001. He was also a consultant and director of YouGov from 2000, remaining in both positions until his election as an MP in 2005.

Notably, on 3 December 2010, Duddridge was permitted to reply on HM Government's behalf from the Despatch Box during an Adjournment debate, a rarity as Commons Whips — particularly Government Whips — by convention do not speak in the Chamber.[2]

James Duddridge voted in favour of the Marriage (Same Sex Couples) Bill at both its second reading in February 2013[3] and its third reading in May 2013.[4]

Duddridge is seen as a hardline Eurosceptic having suggested in Parliament that the Government should tell the European Commissioner to "sod off" rather than pay benefits to Romanians and Bulgarians[6]

During the expenses scandal it was alleged that Duddridge claimed £53,000 over three years for redecoration and mortgage repayments on his second property.[7] Despite owning two properties in London, he still claims a further £11,000 of expenses per year to fund overnight accommodation at London hotels.[8]

In Spring 2014, Duddridge caused controversy by holding his constituency surgery in a branch of Halifax bank, exclusively for Halifax customers.[9]

In April 2015, Duddridge faced criticism for blocking some of his constituents on Twitter. The users who were blocked had politely asked him to clarify his policies and complained that they were left unable to contact their local MP on the social media site.[10]

It was reported that Duddridge earns £6,000 a year from a second job as an advisor to a firm of financial planners.[11]